Specify vectorization level for ex-75 test

diff --git a/tests/examples/step-75.mpirun=1.with_p4est=true.with_trilinos=true.output b/tests/examples/step-75.vectorization_level.leq.1.mpirun=1.with_p4est=true.with_trilinos=true.output
similarity index 100%
rename from tests/examples/step-75.mpirun=1.with_p4est=true.with_trilinos=true.output
rename to tests/examples/step-75.vectorization_level.leq.1.mpirun=1.with_p4est=true.with_trilinos=true.output